The present invention relates to a precision temperature sensor circuit that provides an output voltage that is linearly related to the absolute temperature of the circuit. More specifically, the present invention relates to a precision temperature sensor circuit that eliminates the need for trimming.
Monitoring the temperature of IC chips has long been a concern. Naturally, it is preferable, when possible, to incorporate the temperature sensor into the IC. It is common to use Bipolar Junction Transistors (BJT's) in temperature sensing circuits given the known temperature and current dependence of the forward-biased base-emitter junction voltage thereof. Specifically, the temperature can be measured by subtracting two voltages at two different bias currents in a known ratio.
Such temperature sensors make use of the relationship between the BJT's base emitter voltage to its collector current:
      V    BE    =            kT      q        ⁢          ln      ⁡              (                              I            C                                I            S                          )            where k is Boltzmann's constant, T is the absolute temperature and q is the charge of an electron. Is is the transport saturation current of the transistor. This equations presumes a voltage of a few hundred millivolts on the collector and ignores Early effects.
While conventional temperature sensing circuits provide adequate results, they are typically not precise enough unless they are subjected to trimming, for example by an external trimming circuit. Naturally, the addition of such an external trimming circuit adds expense and complexity to the circuit.
Thus, it would be beneficial to provide a temperature sensor circuit that provides high precision and avoids the need for trimming.